Engine operating parameters such as air-fuel ratio, spark timing, and exhaust gas recirculation (EGR) may be adjusted to increase engine efficiency and fuel economy and decrease emission including nitrogen oxides (NOx). One factor which may affect the adjustment of such operating parameters is intake air humidity. A high concentration of water in the intake air may affect combustion temperatures, dilution, etc. Thus, control of operating parameters including air-fuel ratio, spark timing, EGR, and the like based on humidity can be used to improve engine performance.
However, ensuring that an intake humidity sensor is functioning as desired may be challenging. One example approach for diagnosing a humidity sensor is illustrated by Xiao et al. in U.S. Pat. No. 7,715,976. Therein, humidity sensor degradation is determined based on a comparison of an intake humidity estimated by a first humidity sensor in the intake manifold with an exhaust humidity estimated by a second humidity sensor in the exhaust manifold and an ambient humidity estimated by a third humidity sensor located outside of the engine. The sensor readings are compared during conditions when all the sensor readings are expected to be substantially equal, such as during engine non-fueling conditions in which an EGR valve is closed. If the readings of all three sensors differ by more than a threshold, humidity sensor degradation may be determined.
However, the inventors herein have identified a potential issue with such an approach. The accuracy of determining degradation of an intake humidity sensor may depend on the proper functioning of the other intake humidity sensors. Furthermore, not all vehicles may be equipped with enough humidity sensors to carry out the above-described method.
Thus, the inventors herein have developed systems and methods to at least partially address such issues. In one example, a method is provided, comprising in response to shutdown of an engine configured to propel a vehicle, and to conditions being met for calibrating an intake humidity sensor positioned in an intake manifold of the engine, requesting a humidity estimate from one or more weather devices; and calibrating the intake humidity sensor based on a confidence level in the one or more weather devices and a difference between the humidity estimate and an intake humidity sensor measurement. In this way, the intake humidity sensor may be calibrated at an opportune time, from a weather device associated with a confidence level to further increase robustness of the intake humidity sensor.
As an example, conditions being met for calibrating the intake humidity sensor include an indication that a transmission of the vehicle configured to transfer torque from the engine to one or more wheels of the vehicle is in a park mode of operation, and further responsive to an indication that a threshold duration has elapsed since the engine shutdown and the indication that the transmission is in the park mode of operation. In some examples, the threshold duration may be variable, depending on environmental conditions. In some examples, conditions being met for calibrating the intake humidity sensor may include an indication that the vehicle is not in an environment where the vehicle is exposed to environmental precipitation. The intake sensor may in some examples comprise a dielectric or capacitive humidity sensor coupled with a temperature sensor and mass air flow or mass air pressure sensor.
As another example, the confidence level in the one or more weather devices may be based at least in part on a source or location of the one or more weather devices.
In one example, calibrating the intake humidity sensor based on the confidence level in the one or more weather devices and the difference between the humidity estimate and the intake humidity sensor measurement further comprises calibrating the intake humidity sensor responsive to the difference between the humidity estimate and the intake humidity sensor measurement being greater than a first threshold difference when the confidence level is high; calibrating the intake humidity sensor responsive to the difference between the humidity estimate and the intake humidity sensor measurement being greater than a second threshold difference when the confidence level is medium; calibrating the intake humidity sensor responsive to the difference between the humidity estimate and the intake humidity sensor measurement being greater than a third threshold difference when the confidence level is low. In such an example, the first threshold difference may be smaller than the second threshold difference, which may be smaller than the third threshold difference.
In some examples, the high confidence level includes locations comprising an end of a vehicle assembly line where the vehicle is being assembled, and a dealership of the same make as the vehicle; where the medium confidence level includes locations comprising a personal home of an operator of the vehicle; where the low confidence level includes locations other than the end of the vehicle assembly line, the dealership of the same make as the vehicle, and/or the personal home of the operator of the vehicle, where said low confidence level does not include crowd-sourced data; and wherein crowd-sourced data from a plurality of weather devices includes either the high confidence level, the medium confidence level, or the low confidence level.
In further examples, the one or more weather devices are positioned external to, and removed from, the vehicle. The one or more weather devices may be connected to at least an internet, for example. Furthermore, requesting the humidity estimate from one or more weather devices may include a controller of the vehicle sending a wireless request for the humidity estimate to the one or more weather devices, and wherein the controller further receives the humidity estimate wirelessly from the one or more weather devices.
In this way, an intake humidity sensor may be routinely calibrated throughout the lifetime of the vehicle.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.